DE 10 2005 005 127 A1 discloses an electrical contact and a process for the production thereof. Said document describes an electrical contact for the cold contact-making technique, comprising a metallic substrate which is provided with a coating. The coating is formed from a dispersion of particles of carbon and/or a polymer in a metal. According to this solution, the electrical contact is preferably in the form of a plug contact. The cold contact-making technique involves the two joining partners being pressed together, which can also assume the form of an insulation displacement connection or is provided by a press-fitting technique. Thus, by way of example, a pin is inserted into a terminal or a sleeve which has a coating in which chip formation can occur. According to DE 10 2005 005 127 A1, either one joining partner or both joining partners can be provided with a coating.
DE 10 2005 062 601 A1 relates to an electrical appliance with a lubricated joint and also to a process for lubricating such a joint. According to this solution, an electrical appliance, in particular a control unit, is provided at at least one joint with a first joining partner, in particular a sleeve, which interacts with a second joining partner, in particular a pin. The joint comprises a seam between the two partners to be joined, in which seam an at least partially solidified lubricant is present. The lubricant may be a multi-component substance, wherein the hardened lubricant at least partially outwardly seals the joint at a, preferably axial, end of the joint.
The solidified lubricant bonds at least one metallic chip.
A substance called “Glicoat SMD F2 (LX)” is known from Glicoat SMD Organic Solderability Preservatives (OSP) www.electrochemicals.com), and is used for coating electrical contact elements and printed circuit boards, cf. U.S. Pat. No. 5,498,301 and U.S. Pat. No. 5,560,785. Appropriate OSP coatings, e.g. on the basis of phenylimidazoles or benzimidazoles, are also known from other manufacturers, e.g. Enthone.
In the press-fitting technique, a solderless electrical connection is produced between the connecting pin of a plug strip of another component and a metalized hole in a printed circuit board (sleeve). The connecting pin has a solid or elastic press-fitting zone, the geometry of which is generally manufacturer-specific. Said press-fitting zone undergoes plastic and elastic deformation as it is pressed into the printed circuit board sleeve, and adapts to the diameter of the sleeve. The pin is thereby directly contact-connected with the sleeve.
The printed circuit board sleeve consists essentially of copper, with an overlying further coating as a surface for preventing copper oxidation. Said further coating may be a hot tin plating or a chemically deposited metallization, for example nickel or gold or nickel/gold or tin or silver. In addition, the further coating can be an organic passivation layer, a so-called OSP (organic surface passivation) “material”. The press-fitting zone of the connecting pin usually consists of a copper base material and is usually metalized by electrodeposition. If said electrodeposited metallization is produced from tin, there is a risk that so-called tin whiskers may form. These are acicular tin single crystals having a diameter of a few μm and a length of up to several μm. As a result of these conductive whiskers, there is a risk of a short circuit between open contacts which lie closely together on the printed circuit board or between the connecting pins. If said electrodeposited metallization of the connecting pins is produced from other, for example harder, surfaces, such as nickel or gold or silver, there is a risk that inadmissible damage may occur to the printed circuit board as the connecting pins are being pressed in.
In the case of the insulation displacement technique, which is used as an alternative to the press-fitting technique, a solderless electrical connection is likewise produced between, for example, the wire of a component or of a lead frame and a metalized insulation displacement terminal. The insulation displacement terminal has a solid or elastic V-shaped notch, the geometry of which is generally manufacturer-specific. Said insulation displacement terminal and the wire undergo plastic and elastic deformation as the wire is pressed into the V-shaped notch of the insulation displacement terminal, and adapt to one another in terms of their contour. The wire is thereby directly contact-connected with the insulation displacement terminal.
The wire usually consists of copper or copper alloys or steel, with an overlying further coating as a surface for preventing oxidation. By way of example, said further coating for preventing oxidation may be an electrodeposited metallization, for example copper and tin or copper/nickel and tin. Within the insulation displacement technique, the insulation displacement terminal usually consists of a copper base material and, if appropriate, can be metalized by electrodeposition.
If one of the two surfaces is produced from tin, there is a risk that so-called tin whiskers may form. These are acicular tin single crystals having a diameter of a few μm and a length of up to several mm. As a result of these conductive whiskers, there is a risk of a short circuit between open contacts which lie closely together. If the electrodeposited metallization is produced from another, for example harder, material, for example nickel, gold or silver, there is a risk that no gas-tight connections will be produced when the insulation displacement technique is used. If the surface of the insulation displacement terminal is produced from bare copper or one of the alloys thereof, there is a risk of “fretting”, i.e. the wire merges with the insulation displacement terminal much too early and does not reach the desired position, as a result of which the connection is considerably impaired.